The recent and ongoing transition in the dimensions of wafers used in semiconductor device fabrication toward larger diameters and smaller thicknesses has created a need for technology to seal such wafers at the wafer level. In addition to conventional transfer molding processes carried out with solid epoxy resins, International Application WO 2009/142065 discloses a compression molding process that uses a liquid epoxy resin.
However, in transfer molding, the resin is forced through tight areas, which may cause wire deformation. Also, poor filling is more likely to arise as the surface area to be sealed increases. As for compression molding, the difficulty of precisely controlling the molding range at the wafer edge is compounded by the challenge of optimizing the flowability and physical properties of the liquid encapsulating resin when poured into the molding machine. In addition, the transition toward wafers of larger diameter and smaller thickness has given rise to an entirely new concern—wafer warpage after molding, and so good wafer protection is also required.